1. Field of the Invention
The present invention relates to a herbal extract having anti-influenza virus activity, especially relates to a Schisandrae fructus extract for inhibition or prevention of influenza and its application.
2. The Prior Arts
Every year influenza virus causes epidemic of acute respiratory diseases around the world and has become one of the most life threatening pandemic virus. Influenza virus belongs to the family of Orthomyxoviridae and is classified into type A, B, and C on the basis of its antigen of nucleuoprotein, of which influenza virus B and C mainly infect human and variance of these two types of virus mutants is less significant. However, influenza virus A widely infects birds and mammals such as human, pig and horse. Furthermore, antigen of influenza virus A mutants displays a significant variety and new sub-type mutants are evolved frequently so that new mutants may be able to infect a new host. It has been recorded that a few previous global pandemics are caused by influenza virus A, indicating that influenza virus A can cause serious damage to human health among immuno-deficiency patients, and sometimes jeopardizes human life. Currently treatments of seasonal influenza symptoms are mainly supportive cares, and these therapeutics can be divided into four types. The first type of therapeutics is vaccine, the most common practice of preventive method. However, this approach can't produce protective effect against new evolving virus types. The second type of therapeutics is M2 protein inhibitors such as amantadine and rimantadine, in which replication of influenza virus A is inhibited by blocking M2 ion channel to release RNA. However, this group of therapeutics is ineffective against influenza virus B and it causes neurological and psychological side effects as well as causes drug resistance. The third type of therapeutics is neuraminidase inhibitors such as oseltamivir, zanamivir, and peramivir. Neuraminidase is involved in the release of progeny virus from infected cells, by cleaving sugars that bind the mature viral particles. Specifically, neuraminidase cleaves the α-ketosidic bond that links a terminal neuraminic acid residue to the adjacent oligosaccharide moiety, neuraminidase is therefore essential for the movement of the virus to and from sites of infection in the respiratory tract. Zanamivir and oseltamivir inhibit viral neuraminidase, which plays an important role in viral proliferation and is stably present in both influenza viruses A and B, and both agents have been used for the treatment and prophylaxis of influenza viruses A and B. However, zanamivir is an inhaled form and its acceptability is low. Oseltamivi is widely accepted but statistics of WHO study have shown an emerging concern of drug resistance. The forth method is treatment with virus replication inhibitors such as ribavirin, viramidine and T-705. These drugs can block synthetic pathways of virus proteins. Although the above mentioned treatments are used clinically, there are many disadvantages and side effects and virus mutants are continuingly evolving. Therefore, it is important and necessary to develop new drugs for treatment or prevention of influenza virus.
The dried fruits of Schisandra chinensis (Turca) Baill or Schisandra sphenanthera Rehd. et Wils (family of Schisandraceae), named of Wuweizi or Schisandrae fructus in Chinese traditional medicine, are used as an antitussive, tonic, and sedative agent in China and Taiwan. According to the traditional Chinese medicine, characteristics of Schisandrae fructus are mild, with sour and salty taste, and belonging to the lung, kidney, and heart channel tropism. Functions that provided by Schisandrae fructus include astringent action to the lung, nourishment to the kidney, increase of body strength, stopping sweating, and calm of mind. Furthermore, pharmaceutical studies have found that crude extracts of Schisandrae fructus has functions of calmness, hypnotism, protection of neuron cells and liver, anti-oxidation, anti-cancer, lowering blood sugar, enhancement of bone cell growth, and anti-hepatitis B virus activity. Currently chemical constituents found in Schisandrae fructus include lignans, volatile oils, glycosides, organic acids, fatty acids, vitamin C, and vitamin E are isolated, wherein studies of lignans have shown that this ingredient has biological activity of anti-Alzheimer's disease, liver protection, anti-inflammation, anti-oxidation, as well as anti-HIV virus.
Mutants of influenza virus vary significantly and spread rapidly. When a new virulent mutant of influenza virus emerges and causes new type of flu epidemic, this new epidemic may rapidly distribute across borders around the world. Human life will be greatly threatened and global social and economic activities will be impacted. Thus there is a great need to develop effective anti-influenza virus drugs.